Abrasive article



Patented July 5, 1938 PATENT OFFICE ABRASIVE ARTICLE Joseph N. Kuzmick, Passaic, and Lamar S. Hilton,

Bloomfield, N. J., assignors to Raybestos-Manhattan, Inc., Passaic, N. J., a corporation of New Jersey No Drawing. Application April 28, 1936, Serial No. 76,756

7 Claims.

The present invention relates to the manufacture of abrasive articles and more particularly to the manufacture of abrasive articles suitable for both grinding and polishing use.

The principal object of the invention resides in the provision of a new bonding medium for abrasive. articles such as wheels, discs, blocks, pads etc. A further object of the invention resides in the making of novel abrasive products, so bonded as to render .them suitable for both grinding and polishing action, the products being characterized by being solid in body and yet.

compressible and capable of following the contour of the object being abraded.

There are 'two classes of grinding implements in general use, one class consisting of solid, rigid bonded abrasive articles, such as wheels, discs. and the like, the other class embracing-the socalled flexible set-up polishing wheels, which latter include cloth wheels coated with glue and abrasive, prepared annular abrasive cloth mounted on yielding bodies such as rubber, and felt buffing wheels charged with rouge, etc. There is a commercial demand for this latter class of abra-- sive articles in the polishing and abrading of irregularly shaped surfaces; and because of their inherent qualities of being somewhat compressible, these abrasive articles produce in effect a cushion for. the object being abraded, resulting in producing a very highly finished surface, 'free from chatters such as are obtained when a relatively inflexible, hard, solid abrasive wheel is used.

These so-calledflexible, set-up wheels have been open' to serious objection for years due to their'having only a few layers of abrasive particles or granules on the periphery of the wheels, resulting in very short wheel life and necessitating frequent renewal of the abrasive layer with consequent interruption of production. Various methods have been proposed and attempts made to produce solid wheels, as well as attached layers or blocks ofbonded abrasive in substantial thicknesses on resilient cores, to replace these set-up wheels; but, due to one reason or another, none of these products has assumed commercial importance'.

In the practice of the present invention there are produced solid abrasive wheels, as well as wheels mounted on rigid or resilient cores, in which the abrasive granules and the bond are of such substantial volume as to comprise in effect a solid body and meta superficial coating of bonded abrasive particles.

Carothers, Williams, Collins, and Kirby in th Journal of the American Chemical Society of November 5, 1931 at pages 4203 et. seq., describe a syntheticproduct known as chloroprene. Chloroprene is a halogenateddeiivative of acetylene polymers, more specifically 2-chloro-1,3-buta- 6 diene. Chloro-butadiene derivatives are obtained by combination of mono-vinylacetylene and hydrochloric acid, usually in the presence of proper catalytic agents, polymerization progressing from this point, giving various polymers, such as 10 a-polychloroprene, a fairly soft plastic, up to a-polychloroprene, which is a rubbery, transparent, elastic mass. chloroprene polymers are now available commercially under the trade name Duprene. Chloroprene may be used to replace 5 rubber and when so used possesses the known advantages of ofiering greater resistance to the attack of oils and petroleum solvents, corona resistance, etc.

The use of chloroprene as a bond for abrasive 20 products has also been proposed. We have found,

, or stretching characteristic of the chloroprene 35 bond. Since there is very little, if any, adhesion of this bond to the abrasive particles or granules, there is produced under the influence of such centrifugal force an attenuation of the bond. When this occurs the expanded revolving wheel 40 body vibrates, the loosened abrasive particles or granules fall out of their bond envelopes and the wheel then breaks.

We have discovered that the formation of what we believe to be co-polymers of one or more materials. with chloroprene produces a new bonding agent for abrasive articles, having the following unique characteristics: enormous increase in heat resistance, capability of tenacious adhesion to abrasive particles, and'the capability of having its elongation and hardness controlled to any extent desired.

We have discovered that cresol-formaldehydetung oil complexes (hereinafter referred to as CFIO complexes) form co-polymers with chloroprene. These CFTO polymers are soluble in chloroprene, forming therewith plastics capable of further polymerization to transparent bodies ranging from flexible rubbery materials to firm, leathery, but still pliable products. A grinding or polishing wheel formulated with a co-polymer of chloroprene and CFTO complex as a bond is characterized by the following advantages: The binder assumes a leathery but very pliable characteristic. The elongation or stretch of the binder is reduced to as low as 100%, as compared with 800% for straight chloroprene. The resistance to heat is increased to a point where the wheel is unaffected by the heat generated in grinding. The adhesive qualities of the binder are such that continuous flexing during grinding does not set free the abrasive particles prematurely. However, the binder is still capable of being somewhat distended under pressure in grinding or polishing so that any ununiformities in the article being ground are abraded and polished at the same time. In addition, the binder assumes such a physical state that the grinding wheel can be operated at normal grinding speeds without distension resulting in expension and subsequent rupture due to centrifugal force. Fairly thin wheels of this type have been revolved as high as 15,000 surface feet per minute without rupture.

One of the most important advantages manifested is the feature of being able to produce very free, cool cutting wheels and at the same time retain a burnishing or bufiing action equal to the best so-called set-up wheels without the serious disadvantages of the latter type.

In the grinding and polishing of stainless steel fabricated equipment as heretofore practiced, the

welded seams are first abraded with a rigid coarse grain wheel to remove excess metal. The ground surface after this operation is rough and deeply scored. To restore this surface to the original V Parts by weight Crcsol (boiling range 200 to 204) 100 Formaldehyde (aq. s0l., 40% by vol.) 50 Sulphuric acid ,4

These reagents are charged into a suitable jacketed kettle equipped with a reflux condenser. Heat is applied and the reagents boiled with refluxing for approximately thirty minutes, after which time there will be a distinct layer of resin and a layer of water in the kettle. The residual water is removed by decanting or distillation.

The resinous mass is then heated to approximately 160 C. a specimen of which when cooled should be clear and brittle. At this time 100 parts of tung oil is added and heating continued until any desired viscosity is attained. Depending onthe length of heating, the resinous mass may be viscous and sticky or a brittle solid. Five parts of hexamethylenetetramine is then added to the mass, by stirring if the mass is left in a viscous condition or by grinding in a ball mill if the solid brittle modification is used. This CFIO complex is then capable of further polymerization with heat to a tough, leathery, infusible product.

Although the above example calls for a cresol of 200-204 boiling range (substantially meta para) other cresols work equally as well, although they are not quite so reactive. We may use low or high boiling xylenols, crude cresylic acid, or any combination thereof. The amount of tung oil may be varied at will, but we prefer to use from 50 to 200 parts, depending upon the amount of flexibility we desire to impart to the chloroprene polymer.

Other materials are capable of forming copolymers with chloroprene and may be used in accordance with our invention, but perhaps not as advantageously, as for example, phenol alde-.

hyde resins, styrene, resins derived from phthalic anhydride and polyhydric alcohols, and even tung oil alone.

As a specific example of a grinding or polishing wheel formulatedwith a co-polymer of chloroprene and CFTO complex, we may use the following materials in the proportions specified:

Parts by weight The Duprene and the CFTO complex are first mixed on rubber mill rolls until the heat of mastication dissolves the C'F'IO complex in the Duprene, forming a transparent plastic. The zinc oxide, magnesium oxide, rosin and sulphur are added and rolled until dispersed homogeneously throughout the mass. The abrasive grains are then added in small increments until absorbed and distributed uniformly, forming a plastic sheet. Wheels or discs may then be cut, punched, or otherwise formed from this sheet. The formed articles are then heated from 1 to 5 hours at 310 F. to further polymerize the co-pclymers, as for example between press platens or in a suitable oven.

The use of zinc oxide, magnesium oxide, rosin and sulphur as activating ingredients is well known to those versed'in the art of compounding chloroprene.

It is to be understood that we do not limit ourselves to the proportions cited, as all or any of them may be varied and still remain within the scope of this invention. We have found, however, that 10% to 50% of the CFIO complex by weight ofthe chloroprene polymer are the most desirable proportions. In these proportions the tensile strength remains substantially constanuin' the order of 2200 to 2500 pounds per square'inch, whereas the elongation decreases and the hardness increases in direct proportion to the amount of CFTO complex used. This feature makes it practical to formulate polishing wheels to-any degree of resiliency desired.

We also do not limit ourselves to mixing on rolls, as it is advantageous in specific cases to mix by other'methods to eliminate the crushing action of mixing rolls on the abrasive grains. We canaccomplish this'by dissolving the edpolymers in a solvent, as for example, xylol or benzol, and stirring in the abrasive grains in a dough mixer with subsequent elimination of said solvent. As an alternative, we have produced water dispersions of the co-polymers by the use of bentonite clay, casein, glue, etc., as is well known to those versed in the art, and stirring in the abrasive particles in a dough mixer, with subsequent removal of the water by drying.

We claim:

1. A. solid and compressible abrasive article comprising abrasive particles bonded with a copolymer of chloroprene and a synthetic resin, the synthetic resin acting to controllably reduce the elongation or stretch of the chloroprene.-

2. An abrasive product comprising abrasive grains bonded with a composition of chloroprene and a cresol-formaldehyde-tung oil complex.

3. An abrasive product comprising abrasive particles bonded with'chloroprene and a cresolformaldehyde-mug oil complex, the cresolformaldehyde-tung oil complex being from 10% to by weight of the chloroprene.

4. An abrasive product comprising abrasive particles bonded with chloroprene and a cresolformaldehyde-tung oil complex, the cresolformaldehyde-tung oil complex being from 10% to 50% by weight of the chloroprene, and the bond being of the order of 9% by weight of the abrasive particles.

5. A solid and compressible abrasive product comprising abrasive particles distributed and incorporated in a polymerized plastic consisting of a mixture of chloroprene and a synthetic resin, the synthetic resin acting to controllably reduce the elongation or stretch of the chloroprene.

6. A solid and compressible abrasive article comprising abrasive particles bonded with a copolymer of chloroprene and a synthetic resin, the synthetic resin acting to controllably reduce the elongation or stretch of the chloroprene, the synthetic resin being from 10% to 50% by weight of the chloroprene.

'7. A solid and compressible abrasive article comprising abrasive particles bonded with a copolmer of chloroprene and a synthetic resin, the synthetic resin acting to controllably reduce the elongation or stretch of the chloroprene, the synthetic resin being from 10% to 50% by weight of the chloroprene, and the bond being of the order of 9% by weight of the abrasive particles.

JOSEPH N. KUZMICK. LAMAR S. HILTON, 

